1. To compare the corneal epithelial defect healing time between diabetic patients receiving and not receiving supplementary oxygen after vitrectomy.
2. To determine whether factors such as age, duration of diabetes, duration of surgery and level of glycemic control have any influence on corneal epithelial wound healing time in diabetic patients receiving and not receiving supplementary oxygen post-vitrectomy.

This study aims to determine whether systemic oxygen therapy delivered through face mask would have beneficial effects on the healing of corneal epithelial wound in post-vitrectomy diabetic patients. It will be a prospective, randomised interventional clinical study conducted on diabetic patients indicated for vitrectomy. Rationale of this study is to see if systemic oxygen delivered via face mask will hasten the resolution of corneal epithelial defects, which may either be iatrogenic (surgically-induced intra-operatively to enable clearer visualisation for the surgeon) or spontaneous (due to corneal epithelial fragility which is commoner in diabetics)

Inclusion Criteria:

• diabetic patients aged 18 years and above planned for pars plana vitrectomy that required intra-operative corneal epithelial debridement to allow better surgical visualisation of the fundus were recruited within the study duration

Exclusion Criteria:

• pre-existing ocular surface or corneal disease, recent eye surgery within one month from the vitrectomy, glaucoma and if the patients have any contraindications to oxygen therapy (e.g. chronic obstructive pulmonary disease).